1. Field of the Invention
The present invention relates generally to an air conditioner system for an automotive vehicle. More specifically, the invention relates to an air conditioner system which can automatically adjust blower speed to control air flow rate. Further particularly, the invention relates to an air conditioner system which allows the voltage applied to a blower motor to fluctuate after difference between the cabin temperature and the set cabin temperature become less than a predetermined value.
2. Description of the Prior Art
Various automotive air conditioner systems, which automatically adjust discharge air temperature and air flow rate to achieve comfortable conditions in a vehicular cabin, have been proposed. The Japanese Patent First (unexamined) Publication (Tokkai Sho.) No. 57-140216 discloses such an automatic air conditioner system. In the disclosed system, the voltage applied to a blower motor is controlled on the basis of temperature in the vehicular cabin. The voltage is decreased gradually as the cabin temperature approaches to the set cabin temperature. Thereafter, when difference between the cabin temperature and the set cabin temperature is less than 2.degree. C., the voltage applied to the blower motor fluctuates periodically so that the rate of the conditioning air supplied to the vehicular cabin increases and decreases periodically. By this operation, the occupants of the vehicle feel a comfortably fluctuating breeze.
However, noise is produced by fluctuations of air flow rate and of rotating speed of the blower motor in such a conventional system. Therefore, although the occupants can feel a comfortably fluctuating breeze, they hear the distracting noise.